To reduce an internal resistance of a bearing, which internal resistance is caused, for example, by static or sliding friction, lubricant, such as, for example, bearing oils or greases are used. In rolling-element bearings wherein a first bearing part is movable relative to a second bearing part via rolling elements, the lubricant is needed, for reducing the inner resistance, in particular in the region of the rolling elements as well as at raceways for the rolling elements. So that the lubricants do not escape from the rolling-element bearing, in particular during operation, appropriate seals are provided on rolling-element bearings.
The service life of lubricants is often limited and can be dependent on, among other things, operating parameters of the rolling-element bearing, such as, for example, operating temperature, rotational speed, and bearing pressure, as well as ambient media, such as gases (for example, oxygen), solids (for example, salts), or liquids (for example, water). Furthermore, despite a sealing of the bearing, lubricant sometimes escapes from the bearing. Therefore the lubrication effect of a lubricant of a bearing decreases with increasing operating time of the bearing. As a result the inner resistance or the inner friction of the bearing, and thus the wear of the bearing, increases. Accordingly, to avoid excessive wear of the bearing and to ensure a lowest possible internal resistance of the bearing, care should be taken to avoid operating the bearing with insufficient or inadequate lubricant.
In order to ensure that the bearing is supplied with sufficient lubricant, many bearings include connectors for lubricant pumps, such as, for example, lubrication nipples. Via such nipples fresh lubricant is pressable into the interior of the bearing, for example, via a lubricant pump. It can be provided that old or used lubricant whose tribological properties are compromised, for example, by the intake of abrasion particles, is thereby displaceable out of the bearing.
In particular with large bearings that are subjected to a high mechanical load, a sufficient supplying of lubricant is particularly important since such bearings are often components of a large system, such as, for example, a wind turbine, and a failure of such a bearing results in high costs. Thus, for example, the failure of a wind turbine causes costs to the user for the duration of the failure since the wind turbine produces no current. Furthermore, repairing or replacing such a bearing is expensive since the components of such a wind turbine may sometimes weigh many tons. A disassembling and subsequent assembling of the bearing is therefore only possible by using special devices and is therefore very cost-intensive. For this reason an undersupplying of lubricant is to be avoided with bearings of this type.
For ensuring a regular supplying of the bearing with lubricant, automatic lubrication devices are known that supply the bearing with lubricant according to a prescribed maintenance plan or schedule. Disadvantageously, such lubrication devices do not recognize the actual lubricant need, and lubricants are only provided by them based on experience values or calculations. Particular operating conditions, such as, for example, lubricant leakages, contamination of the lubricant, e.g., due to abrasion of bearing components, increased need of lubricant due to particular load states of the bearing or gumming of the lubricant, are not taken into account by these lubrication devices. Accordingly an undersupplying of the bearing with lubricant, for example, can result with such lubricant devices, due to which undersupplying the wear of the bearing is increased. In the worst case this can lead to damage to the bearing. A too high forecast of the lubricant requirement of the bearing, on the other hand, can also result in an oversupplying of the bearing with lubricant. Such a state is also disadvantageous since the operability of the bearing is thereby possibly reduced.